This invention relates to the sizing of textile yarns, and more particularly to melt sizing with compositions later removable by aqueous means.
The art of textile sizing contains many examples of solutions and dispersions of sizes in water and/or organic solvents. Such compositions inevitably require a slow and expensive drying step after application to yarns. A few examples are known of melt sizes, which do not require removal of solvent, these sizes being based in general upon waxes and other water-insolubles. U.S. Pat. No. 3,466,717 is directed to the application of such a wax-based melt size, removable only by non-aqueous solvents after processing. Besides this restriction, wax sizes have the further deficiency that they lack the film strength, adhesion, flexibility, and ready variability and control of melt viscosity which are inherent in the tougher polymer-based melt sizes of the present invention.
No quick-setting water-soluble melt sizes are known to exist in the art.
Polymers high enough in molecular weight to be good film formers generally give melts having excessively high viscosities and slow solidification rates. Such polymers, if applied as melt sizes, would therefore be expected to flow poorly onto and throughout the fibers of a yarn, and to require application of excessive cooling means and times for solidification. Indeed, the film-forming polymers of the present invention failed completely until the discovery of melt modifiers capable of reducing the melt viscosities and speeding the solidification of the melts to tough and non-sticky films.